Abstract

A Brillouin-scattering-based distributed sensing system has been used for in-situ strain measurement during the curing of AS4-3501 composite panels. It has a pulse length of 1.5 ns, which is equivalent to spatial resolution of 15 cm and read-out resolution of 5 cm. Distributed Brillouin scattering sensors have been used to monitor either tempera- ture or strain for concrete structures, dams, and fiber cables by NTT Transmission System Labs (Japan) and Ecole Polytechnique Federale de Lausanne (EPFL) groups with spatial resolutions .1 m. We report the first application for a Brillouin scattering sensor in a composite curing process. The challenges for this application are the requirements of cen- timeter spatial resolution due to the small size of the composite material; simultaneous temperature and strain measurement during the fast tem- perature changing process of the curing, and short signal processing times. We present experimental results on strain measurements from optical fiber embedded in the eight-ply panels during the heat-up, iso- therm, and cool-down stages of the cure process. The materials studied are 177°C cure thermo-set materials used extensively in the manufac- ture of composite parts for the aerospace industry. The distributed sen- sor can detect the reaction advancement by measuring the cure shrink- age at the gelation and vitrification stages. Shrinkage is then correlated with the degree of cure data from a differential scanning calorimeter (DSC). The thermal response of the solidified composite during cooling is profiled. Details of the data processing of the Brillouin-scattering- based distributed sensor to obtain the strain variations as a function of cure temperature, time, and location are explained. © 2002 Society of Photo-

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.